In a display comprising a plasma display panel (hereinafter also referred to as “PDP”), such as a television (plasma television), an optical sheet (optical member, front filter) are situated on the observer side relative to a light source such as a PDP. The optical sheet has various functions and acts to control light from a source (image light source) so as to output clear and proper image light towards the observer side.
Such an optical sheet is made of a laminate of layers having different functions (features). For example, the optical sheet disclosed in Japanese Laid-Open Patent Publication No. 2006-189867 makes it possible to improve image light in transmittance (luminance) and in contrast (light-dark ratio).
Because of the recent strong demand for displays improved in fineness and performance, however, there is a need to enhance contrast more greatly than the conventional optical sheet described in Japanese Laid-Open Patent Publication No. 2006-189867 can achieve.